Temperature dependent charge transport in electrostatically doped poly[benzimidazobenzophenanthroline] thin films

AbstractCharge transport in electrostatically doped poly[benzimidazobenzophenanthroline]‐BBL thin films in a field‐effect transistor geometry were investigated in the temperature range 150 K < T < 370 K. At low temperatures activation and hopping transport mechanisms dominated, while phonon scattering dominated at high temperatures. The activation energies (EA) were found to lie in the range 140 meV < EA < 400 meV implying the existence of deep traps within the polymer bandgap of 1.8 eV. Two quasi‐linear dependencies of EA on the gate voltage (Vg) were observed with EA decreasing as Vg increased. An unexpected “metallic‐like” transport characteristic appeared for T > 335 K which depended on Vg. Enhanced electron delocalization combined with increased carrier density could be responsible for this “metallic‐like” behavior. Our results show that the existence of deep traps with multiple energy distributions, combined with increased carrier density led to the unusual temperature dependence of charge transport observed in BBL.

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